U.S. patent number 5,146,746 [Application Number 07/807,765] was granted by the patent office on 1992-09-15 for loading/unloading control apparatus for industrial vehicles.
This patent grant is currently assigned to Kabushiki Kaisha Toyoda Jidoshokki Seisakusho. Invention is credited to Katsumi Nagai, Teruyuki Nishimyou.
United States Patent |
5,146,746 |
Nagai , et al. |
September 15, 1992 |
Loading/unloading control apparatus for industrial vehicles
Abstract
A loading/unloading control apparatus for a industrial vehicle
control the discharge capacity of a variable displacement type
hydraulic pump in accordance with the detected result of the amount
of load applied to a loading/unloading hydraulic actuator or with a
manual setting by an operator, thereby to obtain the most suitable
working speed of the actuator for loading/unloading operations.
Inventors: |
Nagai; Katsumi (Kariya,
JP), Nishimyou; Teruyuki (Kariya, JP) |
Assignee: |
Kabushiki Kaisha Toyoda Jidoshokki
Seisakusho (Kariya, JP)
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Family
ID: |
17875663 |
Appl.
No.: |
07/807,765 |
Filed: |
December 6, 1991 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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612193 |
Nov 13, 1990 |
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Foreign Application Priority Data
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Nov 20, 1989 [JP] |
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1-299679 |
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Current U.S.
Class: |
60/445; 60/452;
60/427; 60/459; 91/361; 60/465 |
Current CPC
Class: |
F15B
21/087 (20130101); B66F 9/22 (20130101) |
Current International
Class: |
B66F
9/22 (20060101); B66F 9/20 (20060101); F15B
21/08 (20060101); F15B 21/00 (20060101); F16D
031/02 () |
Field of
Search: |
;60/443,445,427,465,452,431,459 ;91/361 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Look; Edward K.
Assistant Examiner: Mattingly; Todd
Attorney, Agent or Firm: Brooks Haidt Haffner &
Delahunty
Parent Case Text
This application is a continuation, of application Ser. No.
07/612,193, filed Nov. 13, 1990.
Claims
What is claimed is:
1. A loading/unloading control apparatus for an industrial vehicle
comprising a variable displacement type hydraulic pump for
supplying hydraulic fluid to a hydraulic actuator, said hydraulic
pump having a displacement varying mechanism for regulating the
discharge capacity of said pump; means for detecting the amount of
load of said hydraulic actuator; means for setting the working
speed of said hydraulic actuator; a selector switch connected
between said load detecting means and said speed setting means for
selectively outputting a signal from either said load detecting
means or said speed setting means; and a controller for outputting
a control signal to said displacement varying mechanism in response
to a signal from said selector switch, wherein said controller,
when receiving a signal from said load detecting means, outputs a
control signal so as to decrease the discharge capacity of said
hydraulic pump as the amount of load increases, and when receiving
a signal from said speed setting means, outputs a control signal so
as to obtain the discharge capacity of said hydraulic pump
corresponding to the speed set by said speed setting means.
2. A loading/unloading control apparatus according to claim 1,
wherein said variable displacement type hydraulic pump is a swash
plate type axial plunger pump.
3. A loading/unloading control apparatus according to claim 1,
wherein said load detecting means is a pressure detector which is
connected to a conduit between said hydraulic pump and said
hydraulic actuator.
4. A loading/unloading control apparatus according to claim 1,
wherein said industrial vehicle is a fork lift truck, and said
hydraulic actuator is a lift cylinder.
5. A loading/unloading control apparatus according to claim 4,
wherein said load detecting means is a strain gauge fixed on a
piston rod of a tilt cylinder.
6. A loading/unloading control apparatus according to claim 1,
wherein said industrial vehicle is a fork lift truck, and said
hydraulic actuator is a tilt cylinder.
7. A loading/unloading control apparatus according to claim 1,
wherein said industrial vehicle is a shovel loader, and said
hydraulic actuator is a dump cylinder.
8. A loading/unloading control apparatus according to claim 1,
wherein said speed setting means is a variable resistor.
9. A loading/unloading control apparatus for an industrial vehicle
having an hydraulic actuator, said apparatus comprising a variable
displacement type hydraulic pump for supplying hydraulic fluid to
said hydraulic actuator, said hydraulic pump having a displacement
varying mechanism for regulating the discharge capacity of said
pump; means coupled to said actuator for detecting the amount of
load on said hydraulic actuator; means for setting the operating
speed of said hydraulic actuator; a selector switch connected
between said load detecting means and said speed setting means for
selectively outputting a signal from either said load detecting
means or said speed setting means; and a controller having an input
coupled responsively to said selector switch and having an output
coupled to said displacement varying mechanism for outputting a
control signal to said displacement varying mechanism in response
to a signal from said selector switch wherein said controller, when
receiving a signal from said load detecting means, outputs a
control signal so as to decrease the discharge capacity of said
hydraulic pump as the amount of load increases, and when receiving
a signal from said speed setting means, outputs a control signal so
as to obtain the discharge capacity of said hydraulic pump
corresponding to the speed set by said speed setting means.
Description
FIELD OF THE INVENTION
The present invention relates to a loading/unloading hydraulic
circuit used for industrial vehicles such as a fork lift truck, a
shovel loader, etc., and, more particularly, to a loading/unloading
control apparatus for controlling the working speed of a hydraulic
actuator such as a lift cylinder.
BACKGROUND OF THE INVENTION
FIG. 1 schematically shows a general conventional loading/unloading
hydraulic circuit in a fork lift truck. In such a hydraulic
circuit, a fixed displacement type hydraulic pump 1 sucks up
hydraulic fluid from an oil tank 3 to supply or discharge the
hydraulic fluid to or from a lift cylinder 5 through a control
valve 7.
In the above-mentioned hydraulic circuit, since the pump is usually
a fixed displacement type, the lifting speed of a piston rod 9 of
the lift cylinder 5, i.e., the lifting speed of a fork (not shown)
attached to the piston rod 9, is generally constant whether the
fork lift truck is under a load or not. This lifting speed is st so
that it will be optimal when cargos are loaded on the fork. As a
result, for example, while the fork lift truck is going to pick up
a cargo from a high location, the lifting speed of the fork is
comparatively low in spite of being unloaded, thereby generating
needless waiting time and decreasing operating efficiency.
SUMMARY OF THE INVENTION
Accordingly, a primary object of the present invention is to
provide a loading/unloading control apparatus which can control the
working speed of a hydraulic actuator such as a lift cylinder,
etc., to thereby reduce waiting time and improve operating
efficiency.
Another object of the present invention is to provide a
loading/unloading control apparatus which can automatically control
the working speed of the hydraulic actuator in response to the
amount of load applied to the actuator.
A further object of the present invention is to provide a
loading/unloading control apparatus in which the working speed of
the hydraulic actuator can be manually controlled.
Yet another object of the present invention is to provide a
loading/unloading control apparatus in which the working speed of
the hydraulic actuator can be either manually or automatically
controlled.
Therefore, the present invention is directed to a loading/unloading
control apparatus for an industrial vehicle comprising a variable
displacement type hydraulic pump for supplying hydraulic fluid to a
hydraulic actuator, the hydraulic pump having a displacement
varying mechanism for regulating the discharge capacity of the
pump, means for detecting the amount of load applied to the
hydraulic actuator, and a controller for outputting a control
signal to the displacement varying mechanism in response to a
signal from the load detecting mean so as to decrease the discharge
capacity of the hydraulic pump as the amount of load increases.
In the arrangement of such an apparatus, the discharge capacity of
the pump is automatically regulated in response to the amount of
load applied to the actuator. That is, under an unloaded condition,
the discharge capacity of the pump is maximized to maximize the
working speed of the hydraulic actuator. As a result, waiting time
is reduced. On the other hand, under a loaded condition, since the
discharge capacity of the pump is suitably decreased in accordance
with the amount of load of the hydraulic actuator, the working
speed of the actuator is optimal for the load or cargo weight.
Also, the present invention is directed to a loading/unloading
control apparatus for an industrial vehicle comprising a variable
displacement type hydraulic pump for supplying hydraulic fluid to a
hydraulic actuator, the hydraulic pump having a displacement
varying mechanism for regulating the discharge capacity of the
pump, means for setting the working speed of the hydraulic
actuator, and a controller for outputting a control signal to the
displacement varying mechanism in response to a signal from the
speed setting means so as to obtain the discharge capacity of the
hydraulic pump corresponding to the speed set by the speed setting
means.
In such an apparatus, when an operator manually inputs a desired
speed to the speed setting means, the discharge capacity of the
pump will correspond to the input value, and the hydraulic actuator
can drive at the desired speed.
Further, the present invention is directed to a loading/unloading
control apparatus for an industrial vehicle comprising a variable
displacement type hydraulic pump for supplying hydraulic fluid to a
hydraulic actuator, said hydraulic pump having a displacement
varying mechanism for regulating the discharge capacity of the
pump, means for detecting the amount of load applied to the
hydraulic actuator, means for setting the working speed of the
hydraulic actuator, a selector switch connected between the load
detecting means and the speed setting means for selectively
outputting a signal from either the load detecting means or the
speed setting means, and a controller for outputting a control
signal to the displacement varying mechanism in response to a
signal from the selector switch, wherein the controller, when
receiving a signal from the load detecting means, can output a
control signal so as to decrease the discharge capacity of the
hydraulic pump as the amount of load increases, and when receiving
a signal from the speed setting means, output a control signal so
as to obtain the discharge capacity of the hydraulic pump
corresponding to the speed set by the speed setting means.
With this arrangement, manual or automatic speed control can be
selected for more suitable loading/unloading control.
These and other objects and features of the present invention will
become apparent from the following detailed description in
conjunction with the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a circuit diagram of a conventional loading/unloading
hydraulic circuit of a fork lift truck;
FIG. 2 is a circuit diagram of a loading/unloading hydraulic
circuit of a fork lift truck to which a loading/unloading control
apparatus according to a first embodiment of the present invention
is applied;
FIG. 3 is a graph showing the preferable relationship between the
amount of load applied to a hydraulic actuator and the discharge
capacity of a pump;
FIG. 4 is a circuit diagram of a loading/unloading hydraulic
circuit of a fork lift truck to which a loading/unloading control
apparatus according to a second embodiment of the present invention
is applied;
FIG. 5 is a graph showing the preferable relationship between the
value of resistance of a variable resistor and the discharge
capacity of a pump;
FIG. 6 is a circuit diagram of a loading/unloading hydraulic
circuit of a fork lift truck to which a loading/unloading control
apparatus according to a third embodiment of the present invention
is applied;
FIG. 7 is a perspective view of a conventional shovel loader in
which a control apparatus in accordance with the invention may be
installed; and
FIG. 8 is a side-elevational showing of a fork lift truck having a
control apparatus in accordance with the invention.
DETAILED DESCRIPTION OF THE INVENTION
In the following description, like reference characters designate
like or corresponding parts throughout the several views.
Referring now to the drawings, and particularly to FIG. 2, a
loading/unloading hydraulic circuit for a fork lift truck 60 (FIG.
8) incorporated with a loading/unloading control apparatus
according to a first embodiment of the present invention is shown.
This hydraulic circuit comprises an oil tank 7, a hydraulic pump 10
for sucking hydraulic fluid from the oil tank 3, a control valve 7
for controlling the flow direction of fluid discharged from the
pump 10, and a lift cylinder 5 of the fork lift truck 60.
In this embodiment of the present invention, the hydraulic pump 10
is a variable displacement type pump, preferably a swash plate type
axial plunger pump which can vary discharge capacity of the pump by
regulating the angle of a swash plate 12 by means of a displacement
varying mechanism 14. A conduit 16 between the control valve 7 and
the lift cylinder 5 is connected with a pressure detector 18 as
means for detecting the amount of load applied to a piston rod 9 of
the lift cylinder 5. However, it should be understood that the
pressure detector 18 can be replaced with other suitable means for
detecting the amount of load, for example a strain gauge fixed on a
piston rod of a tilt cylinder 63 as shown in FIG. 8. The pressure
detector 18 is connected to the input portion of a controller
(e.g., a microcomputer) 20. The output portion of the controller 20
is connected to the displacement varying mechanism 14 of the
hydraulic pump 10, and the controller 10 outputs control signals to
the displacement varying mechanism 14 in response to the signals
from the pressure detector 18 to regulate the angle of the swash
plate 12.
The pressure detector 18 can detect the pressure of hydraulic fluid
in the conduit 16, the detected pressure corresponding to the
amount of load applied to the piston rod 9 of the lift cylinder 5.
Therefore, when signals from the pressure detector 18 are input to
the controller 20, the controller 20 converts the signals into the
amount of load applied to the piston rod 9. In the controller 20,
data indicating the relationship between the amount of load and the
discharge capacity of the pump as shown in FIG. 3 are previously
stored, and the controller 20 determines a suitable discharge
capacity of the pump from the amount of load on the basis of the
stored data. Under unloaded conditions, the controller 20 outputs a
control signal to the displacement varying mechanism 14 for
maximizing the capacity of the pump 10. On the other hand, under
loaded conditions, the controller outputs a control signal for
varying the pump discharge capacity to the displacement varying
mechanism 14 so that the pump 10 has a discharge capacity
corresponding to the amount of load actually applied to the piston
rod 9 to incline the swash plate 12 to a desired angle. As a
result, the fork 64 as shown in FIG. 8 connected to the piston rod
9 of the lift cylinder 5 can move up at the maximum speed when it
does not have any cargo. Also, when the fork is carrying cargo, it
can move up at the most suitable speed for the weight of the
cargo.
FIG. 4 shows a loading/unloading control apparatus according to a
second embodiment of the present invention. The arrangement of this
embodiment is the same as that of the first embodiment except that
a variable resistor 30 is connected to the input portion of a
controller 20' in place of the means for detecting the amount of
load such as the pressure detector.
The variable resistor 30 is one means for manually setting the
lifting speed of the fork. The variable resistor 30 can vary the
value of resistance thereof by the rotation of a knob 32, the
resistance value being digitized through an analog/digital
converter 34 and inputted to the controller 20'. The controller 20'
determines the value of resistance of the resistor 30 from the
inputted digital signal, and the discharge capacity of the
hydraulic pump 10 in accordance with the relationship as shown in
FIG. 5. The controller 20' outputs a control signal to the
displacement varying mechanism 14, whereby the hydraulic pump 10
has the determined discharge capacity. When the pump 10 is operated
with this determined discharge capacity, the piston rod 9 of the
lift cylinder 5 moves up at the speed corresponding to this
discharge capacity of the pump and the lifting speed of the fork is
the speed set by the knob 32 of the variable resistor 30.
Thus, although the working speed of the fork must be set by the
operator, it is advantageous that the speed can be set depending on
the kind of cargo. For example in case of fragile cargo such as
glass, it is possible to minimize the working speed in order to
prevent the breakage thereof.
In the second embodiment, the variable resistor 30 can be replaced
with a digital switch as the means for setting the working
speed.
FIG. 6 shows a third embodiment of the present invention. The third
embodiment includes a pressure detector 18 as the means for
detecting the amount of load, a variable resistor 30 as the means
for setting the working speed, and a selector switch 40 for
selectively supplying the signals from either the pressure detector
or the variable resistor to the input portion of a controller 20".
Therefore, it will be understood by the those skilled in the art
that the lifting speed control of the fork can be selected from
either automatic control in response to the amount of load or
manual control by simply changing the selector switch 40.
In this way, the third embodiment has both features of the first
and second embodiments as above mentioned, thereby covering various
needs of the user.
Although all the above-mentioned embodiments are applied for
controlling the working speed of the lift cylinder 5 of a fork lift
truck 60 the present invention is not limited to this application.
For example, the present invention may be applied to a tilt
cylinder 63 of a fork lift truck 60 as illustrated in FIG. 8, or
any hydraulic actuators of other industrial vehicles such as a dump
cylinder 31 of a shovel loader 50 as illustrated in FIG. 7.
It is thought that the present invention and many of its attendant
advantages will be understood from the foregoing description and it
will be apparent that various changes may be made in the form,
construction and arrangement thereof without departing from the
spirit and scope of the invention.
* * * * *